Method for adaptive interleaving in a wireless communication system with feedback

ABSTRACT

The present invention pertains to a transmitter that can exploit feedback to help it organize information which is subsequently sent to a receiver. More specifically, the transmitter receives a feedback signal from the receiver and then uses data about a channel in the feedback signal to adapt at least one of a coding, interleaving and modulating scheme to organize information which is subsequently transmitted to the receiver. In this way, the transmitter can obtain the best match of a channel and a given information payload.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless communication system withcoding, interleaving and modulation that has transmitters that canexploit feedback about a state of a channel in choosing how to organizeinformation.

2. Description of Related Art

The use of coding, interleaving and modulation is prevalent in bothcurrent and proposed wireless communication systems. Also, the currentand proposed wireless communication systems can have different forms ofradio access including Time Division Multiple Access (TDMA) with orwithout frequency hopping, Code Division Multiple Access (CDMA),Orthogonal Frequency Division Multiplexing (OFDM), Multi-Carrier CDMA(MC-CDMA), etc. In addition, the current and proposed wirelesscommunication systems enable many different forms of feedback signaling,ranging from power control commands to complete channel stateinformation. These main ingredients can be combined in different wayswithin the current and proposed wireless communication systems. To helpdescribe how these main ingredients can be combined within traditionalwireless communication systems, reference is made to FIG. 1.

FIG. 1 (PRIOR ART) is a block diagram showing the basic components of atraditional wireless communication system 100 that includes asingle-antenna transmitter 102 (only one shown) and a single-antennareceiver 104 (only one shown). One skilled in the art will appreciatethat it is relatively straightforward to extend this diagram and thedescription below to take into account multiple-antenna transmittersand/or multiple-antenna receivers. As shown, the transmitter 102 has acoder 106, an interleaver 108 and a modulator 110 that work together totransmit a radio signal 112 which passes through a channel and isreceived by the receiver 104. The received radio signal 112 is made upof many components, including the desired signal, own cell interference,other cell interference, adjacent carrier interference, and internalreceiver noise. In baseband, the received radio signal 112 can bewritten as:r _(n) =C*s _(n) +i _(n) +w _(n),where s_(n) refers to the desired signal information symbols, C=[C₀, . .. , C_(M-1)] is a vector of M channel taps representing the state of thechannel, * indicates a filter, or convolution, operation, i_(n) refersto one or more co-channel and adjacent channel interference signals thatthe receiver 104 treats explicitly (for instance by whitening or jointdetection), and w_(n) refers to all other noise.

The format of the desired signal s_(n) may be TDMA, CDMA, OFDM, MC-CDMA,etc . . . First consider the case of TDMA. On each slot, assume that thereceiver 102 computes an estimate of the signal-to-noise-ratio (SNR).The SNR is presumed to account for the particular capabilities of thereceiver 104. That is, if the receiver 104 suppresses co-channel oradjacent channel interference, then that is reflected in the SNR. In anon-frequency hopped TDMA system, the slot SNR's reflect the timeevolution of the desired signal channel, interference, etc . . . And, ina frequency hopped TDMA system, the SNR's reflect the frequencyselectivity of the channel, and the different interference level on eachhop. Next consider the case of OFDM and MC-CDMA, where it is assumedthat the receiver 104 computes an SNR for each carrier. These SNRsreflect the frequency selectivity of the channel, and the differentinterference level on each carrier. In all of these cases associatedwith TDMA, CDMA, OFDM, MC-CDMA, etc . . . , the receiver 104 sends theSNR information in a feedback signal 114 to the transmitter 102.

Unfortunately, the traditional transmitter 102 does not use the SNRinformation in the feedback signal 114 to help organize the informationit subsequently transmits in a radio signal 116 to the receiver 104.Instead, the transmitter 102 uses a randomizing strategy or some otherstrategy to send the information in radio signal 116 to the receiver104. A more detailed discussion is provided next about some of thedifferent ways the transmitter 102 can use a randomizing strategy orsome other strategy to send the information in radio signal 116 to thereceiver 104.

First, assume the transmitter 102 protects the information by using arandom error correcting code. The random error correcting code caninclude convolutional codes, turbo codes, binary block codes or lowdensity parity check codes (for example). Also, assume that thetransmitter 102 uses trellis coded and block coded modulation schemes.These coding and modulation schemes are designed, and work best for thetransmitter 102 in a non-fading environment where the presence of anoise process is independent from bit to bit (or symbol to symbol).However, in a fading environment for these methods to work well, thetransmitter 102 typically resorts to a randomizing strategy which usessome form of interleaving to try and re-create a favorable scenario thattakes advantage of diversity to transmit the information in radio signal116 to the receiver 104. The term diversity is used herein to cover thevariation in the desired signal's channel conditions, as well as thelevel of interference and its channel conditions, which are all seenfrom the vantage point of the receiver 104.

For instance, in a non-frequency hopping TDMA system, the transmitter102 interleaves the bits from a codeword over multiple slots and withineach slot to benefit from time diversity. In a frequency hopping TDMAsystem, the transmitter 102 interleaves the bits from a codeword overmultiple hops, to benefit from frequency diversity. This is typicallydone in addition to time diversity. For a more detailed discussion aboutthe relationship between coding and hopping reference is made to U.S.Patent Application Serial No. 2002/0126736 entitled “Methods and Systemsfor Selective Frequency Hopping in Multiple Mode Communication Systems”.The contents of this document are incorporated be reference herein.

Similarly, in an OFDM or MC-CDMA system, the transmitter 102 interleavesthe bits from a codeword over multiple carriers. Thus, the guidingprinciple of a randomizing strategy that uses interleaving is to subjecteach codeword to a diversity of channel conditions, some of which arefavorable, to give the receiver 104 a good chance of decoding thatcodeword successfully.

Now assume the transmitter 102 protects the information by using a bursterror correcting code. The burst error correcting code includes binarycodes such as Fire codes, and non-binary codes such as Reed-Solomoncodes. In this situation, the strategy is essentially the opposite ofrandomizing. That is, for the case of a binary code, the transmitter 102places neighboring bits on the same modulation symbol, and on the sameslot or on the same tone. That way, if conditions at the receiver 104are bad on a certain modulation symbol or slot or tone, a burst errormay occur, which a decoder located therein is well suited to handle.Similarly, for the case of a non-binary code, the bits representing anon-binary code symbol (which may or may be the same size as amodulation symbol) are placed on the same modulation symbol, and on thesame slot or on the same tone. As can be seen, the transmitter 102 andthe burst error correcting code scheme described in this example do notuse the SNR information in the feedback signal 114 to help organize theinformation it subsequently transmits in radio signal 116 to thereceiver 104.

Now assume the transmitter 102 protects the information by using errorcontrol coding which is found in differential modulation and codingschemes. Typically, differential modulation is used for reasons otherthan coding. But, in here differential modulation is viewed from thecoding perspective. For instance, consider the IS-136 standard, whichuses Differential Quadrature Phase Shift Keying (DQPSK). In this case,the transmitter 102 while in speech mode protects certain informationbits by coding while other information bits remain uncoded.

It has been found that the performance of DQPSK can be enhanced with theuse of multi-pass demodulation. This enhancement performance isdescribed in U.S. Pat. No. 5,673,291, the contents of which areincorporated by reference herein. Basically, the patent describes anidea where re-encoded DQPSK symbols corresponding to protected bits areused as effective pilots, to help demodulate the received neighboringsymbols.

The multi-pass demodulation scheme itself can also be improved upon asdescribed in an article by A. Khayrallah et al. entitled “InterleaverDesign and Multi-Pass Demodulation,” Proceedings Conference onInformation Sciences and Systems, 2001. The contents of this article areincorporated by reference herein. Using the scheme described in thisarticle, one can provide large performance gains when the originalinterleaver is replaced with one designed specifically to take advantageof the interplay between multi-pass demodulation and the differentialproperties of DQPSK.

It has also been found where it is useful to separate the differentialaspect from the modulation itself. That is, one can use standardcoherent modulation such as Phase Shift Keying (PSK) or QuadratureAmplitude Modulation (QAM) and then impose differential relations amongthe bits before mapping them into modulation symbols. An advantage ofthis is associated with the added flexibility one has to design variousdifferential relations among the bits. Moreover, it has been shown inthe following two documents that such differential schemes can providelarge gains in conjunction with multi-pass demodulation. One document isU.S. Patent Application No. 2001/0033621 and the other document is anarticle by A. Khayrallah entitled “Differential Coding over Bits forHigher Level Modulation,” Proceedings Conference on Information Sciencesand Systems, 2002. The contents of both of these documents areincorporated by reference herein. In these schemes, the basic idea isthat re-encoded bits can act as effective pilots, boosting theperformance of neighboring bits that are connected to them by adifferential relation. As can be seen, the transmitter 102 and thedifferential modulation and coding schemes described in this example donot use the SNR information in the feedback signal 114 to help organizethe information it subsequently transmits in radio signal 116 to thereceiver 104.

From the foregoing, it should be noticed that the traditionaltransmitter 102 even with the availability of extensive information inthe feedback signal 114 still uses only a randomizing strategy or someother strategy like differential modulation and coding to send theinformation in radio signal 116 to receiver 104. The exploitation ofinformation in a feedback signal, to help a transmitter better organizethe information that is transmitted in a radio signal to a receiver is afocus of the present invention.

BRIEF SUMMARY OF THE INVENTION

The present invention pertains to a wireless communication system whichhas a transmitter that can exploit feedback to help it organizeinformation which is subsequently sent to a receiver. More specifically,the transmitter implements one of the schemes of the present inventionso it can exploit feedback about the state of a channel in determininghow to organize information which is then sent to the receiver. Severaldifferent schemes are described herein to help explain how thetransmitter can organize information to exploit the known channelconditions. For instance, the schemes can use random error correctingcodes, burst error correcting codes or differential modulation/codingschemes. An aim of the present invention is to enable a transmitter toobtain the best match of a channel and a given information payload. Thepresent invention is well suited for fixed rate applications, such asspeech coders and streaming media applications. In addition, the presentinvention does not preclude the use of other control mechanisms, such asvarying the rate or the power, which can be considered as an outercontrol in addition to the schemes of the present invention.

The typical scenario described herein is one where a terminal (receiver)sends feedback information about the downlink to a base station(transmitter) on an uplink channel. This can happen in applications suchas streaming and web browsing where the data traffic on the downlink ishigher than on the uplink. The uplink is likely to have the excesscapacity to handle the traffic generated by the feedback. There areother scenarios where the traffic is balanced or higher on the uplink.This includes e-mail and office applications. In such cases, it would bebeneficial for the base station to send feedback to the terminal.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be had byreference to the following detailed description when taken inconjunction with the accompanying drawings wherein:

FIG. 1 (PRIOR ART) is a block diagram of a wireless communication systemthat includes a transmitter which does not exploit information in afeedback signal when it organizes and sends information in a radiosignal to a receiver;

FIG. 2 is a block diagram of a wireless communication system thatincludes a transmitter which does exploit information in a feedbacksignal when it organizes and sends information in a radio signal to areceiver in accordance with the present invention; and

FIG. 3 is a flowchart that shows the steps of a preferred method forenabling a transmitter to exploit feedback about a state of a channel inchoosing how to organize information that is to be sent to a receiver inaccordance with the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 2, there is a block diagram of a wirelesscommunication system 200 that includes a single-antenna transmitter 202(only one shown) and a single-antenna receiver 204 (only one shown)which are both configured in accordance with the present invention. Asshown, the transmitter 202 which can be implemented in a base station(not shown) has a coder 206, an interleaver 208 and a modulator 210 thatwork together to transmit a radio signal 212 which passes through achannel and is received by the receiver 204 (e.g., mobile phone 204).The received radio signal 212 is made up of many components, includingthe desired signal, own cell interference, other cell interference,adjacent carrier interference, and internal receiver noise. In baseband,the received radio signal 212 can be written as:r _(n) =C*s _(n) +i _(n) +w _(n),where s_(n) refers to the desired signal information symbols, C=[C₀, . .. , C_(M-1)] is a vector of M channel taps representing the state of thechannel, * indicates a filter, or convolution, operation, i_(n) refersto one or more co-channel and adjacent channel interference signals thatthe receiver 104 treats explicitly (for instance by whitening or jointdetection), and w_(n) refers to all other noise. The format of thedesired signal s_(n) may be TDMA, CDMA, OFDM, MC-CDMA, etc . . .

The receiver 204 then in a similar manner as described in the BackgroundSection analyzes the received radio signal 212 and sends a feedbacksignal 214 to the transmitter 202. The feedback signal 214 containsinformation about channel conditions like SNRs. Following is a detaileddescription about some different ways the transmitter 202 can use theknowledge about channel conditions in the feedback signal 214 tocomplement a randomizing strategy or another strategy (e.g.,differential modulation and coding schemes) and organize informationthat is subsequently transmitted in radio signal 216 to the receiver204.

Consider the case of OFDM or MC-CDMA. Suppose there are L carriers, andthat the receiver 204 in determining the feedback signal 214 computes avector of L SNRs, denoted as follows:σ=[σ₁, . . . , σ_(L)].Because, the transmitter 202 has knowledge of σ, it can use thisknowledge to organize information in order to best match thecapabilities of its coding, interleaving, and modulation scheme. Asstated earlier, the present invention focuses on how to organize a givenpayload, rather than varying the rate or the power. Those schemes can beconsidered in addition to the schemes of the present invention.

Suppose that the information associated with radio signal 216 isprotected with a random error correcting code. Recall that in the priorart, the traditional transmitter 102 used a random-like interleavingscheme to disperse each codeword's bits over the symbols on the varioustones. Instead, in the present invention, the transmitter 202 can usethe accurate and timely information σ in the feedback signal 214 and arandom-like interleaving scheme to position the codeword's bitsaccordingly. For example, suppose the values σ_(i) are sorted fromsmallest to largest, with indices i₁ to i_(L). As a result, a bit senton a high index tone will be received reliably, while a bit sent on alow index tone will be received unreliably. The transmitter 202 can nowinterleave a codeword's bit to explicitly exploit this knowledge. Forinstance, the transmitter 202 can place the first bit at Tone i₁, thesecond bit at Tone i_(L), the third bit at Tone i₂, the fourth bit atTone i_(L-1), etc, alternating good and bad tones to create a balancedplacement that bests suits a random error correction code. If the codelength is greater than L, then the interleaving pattern can repeat afterL bits. Since the transmitter 202 and the receiver 204 both know σ, theycan infer the same interleaving pattern, and function properly. Itshould be noted that the code's properties determine its ability toexploit diversity. This means that there is a number L′ beyond whichexposing the codeword bits to more tones does not help the performanceof the decoder within the receiver 204. As such, if L′ is smaller thanL, then the transmitter 202 can choose L′ to define the interleaverscheme instead of L.

In the aforementioned scheme, a balance between pushing as many codebits as possible over the channel and avoiding wasting energy can alsobe achieved by skipping the worst carriers. That is, given the code, itis possible to determine off-line by analysis or experimentation the SNRthreshold below which it becomes detrimental to send code bits orsymbols. In other words, in a list of carriers sorted by decreasing SNR,the end of the list that falls below the threshold would be eliminatedfrom the resource pool. And, the remaining carriers would be madeavailable for transmitting the radio signal 216.

Now suppose that the information associated with radio signal 216 isprotected with a burst error correcting code. This includes binary codessuch as Fire codes, and non-binary codes such as Reed-Solomon codes. Inthis case, the transmitter 202 intentionally places neighboring bits ina single tone, or in a cluster of bad tones. For instance, if 16 QAM isused, the transmitter 202 could place the first 4 bits at Tone i₁, thenext 4 bits at Tone i₂, and so on.

Now suppose that the information associated with radio signal 216 isprotected with differential modulation and coding schemes. In this case,it is possible for the transmitter 202 to choose the specificdifferential relations to suit the state of the channel indicated by thefeedback signal 214. In particular, it is possible for the transmitter202 to help a few very bad tones a lot, or many bad tones each a littlebit. To illustrate this feature, two exemplary schemes are describedbelow where the input bits before the differential encoding are denotedas x, and the output bits after the differential encoding are denoted asy. Bits x may be the output of an error control encoder 206 in thetransmitter 202. And, bits y feed the modulator 210. The actualmodulation may be binary or QAM, PSK etc . . .

Exemplary Scheme 1

Consider a situation where every other tone is bad. In particular, tone1 is bad and tone 2 is good. The bits x₁ that map in Tone 1 are leftunchanged, and the bits x₂ that map onto Tone 2 are encoded as follows:y₁=x₁y ₂ =x ₂ +y ₁where the input bits x₁ and x₂ can be the outputs of a common errorcontrol encoder, or separate encoders in the transmitter 202.

At the receiver 204, the soft values are obtained for y₁ and y₂ from ademodulator (not shown). The soft values are then fed into a Maximum aPosteriori (MAP) decoder (not shown) which corresponds to the abovedifferential equations. A detailed description about a MAP decoder isprovided in the aforementioned article by A. Khayrallah entitled“Differential Coding over Bits for Higher Level Modulation”.

The MAP decoder's output is then fed to a common error control decoder,or separate decoders in the receiver 204. The soft decisions from thedecoder(s) are fed back to a differential decoder as side information ina second or subsequent pass. As a result, the performance of theinformation on tone 1 is improved. It should be appreciated that manycomponents and details associated with the transmitter 202 and thereceiver 204 described above are well known in the industry. Therefore,for clarity, the description provided herein omits those well knowncomponents and details that are not necessary to understand the presentinvention.

Exemplary Scheme 2

Consider a situation where every other third tone is bad. In particular,tone 1 is bad and tones 2 and 3 are good. In this example, the bits x₁that map in Tone 1 are left unchanged, and the bits x₂ and x₃ that arerespectively mapped onto tones 2 and 3 are encoded as follows:y₁=x₁y ₂ =x ₂ +y ₁y ₃ =x ₃ +y ₁where bits x₁, x₂ and x₃ are the outputs of a common error controlencoder, or separate encoders in the transmitter 202.

At the receiver 204, the soft values are obtained for y₁, y₂ and y₃ froma demodulator (not shown). These soft values are then fed into a MAPdecoder (not shown) which corresponds to the above differentialequations. The MAP decoder's output is then fed to a common errorcontrol decoder, or separate decoders in the receiver 204. The softdecisions from the decoder(s) are fed back to a differential decoder asside information in a second or subsequent pass. As a result, theperformance of the information on tone 1 is improved more than in theprevious scheme, due to the simultaneous relation with 2 bits. Thisscheme can be extended to larger sets of equations.

Now consider the case of TDMA. Suppose that a codeword is interleavedover L slots, and that the receiver 204 computes their corresponding SNRvector σ. Without frequency hopping, the SNRs reflect primarily thevarying interference level. With frequency hopping, the SNRs alsoreflect frequency selectivity. The strategies described above withrespect to OFDM and MC-CDMA can also be used to suit this type of code.

From the foregoing, it should also be readily appreciated by thoseskilled in the art that the present invention includes a method 300 thatcan exploit feedback about a state of a channel in choosing how toorganize information in a transmitter 202 with coding, interleavingand/or modulation schemes. The basic steps of the method 300 are shownin FIG. 3. Beginning at step 302, the transmitter 202 receives thefeedback signal 214 from the receiver 204. As described above, thefeedback signal 214 contains data about a state of a channel between thetransmitter 202 and the receiver 204. And at step 304, the transmitter202 exploits the data in the feedback signal 214 to adapt at least oneof the coding, interleaving and/or modulating schemes to organizeinformation that is subsequently transmitted within the radio signal 216to the receiver 204. Several different examples on how this can beaccomplished have been described above.

While particular embodiments of the invention have been described, itshould be understood, however, that the invention is not limitedthereto, since modifications may be made by those skilled in the art,particularly in light of the foregoing teachings. It is, therefore,contemplated by the appended claims to cover any such modifications thatincorporate those features or those improvements which embody the spiritand scope of the present invention. Several of these modifications orextensions to the present invention are described next.

Previously, it was assumed that the feedback signal 214 contained avector of SNRs. This information is typically quantized. Thequantization may be memoryless, or if the SNRs change slowly relative tothe rate of feedback, the quantization may have memory, such as inDifferential Pulse Code Modulation (DPCM) and sigma-delta quantization.Typically, the receiver 204 makes its interleaving decisions based onthe quantized information, to match with the transmitter 202. Coarserquantization enables a leaner feedback, at the expense of moreapproximate matching.

However, in case the SNR information itself is not needed for otherpurposes at the transmitter 202, it is possible to convey theinterleaving information directly in the feedback signal 214. Forinstance, if the number L of tones or slots is small, it is possible forthe transmitter 202 and receiver 204 to keep a list of pre-definedinterleavers that attempt to suit different SNR scenarios approximately.Then, the feedback signal 214 would include the index of the choseninterleaver. In addition, other feedback reducing mechanisms can beimplemented by the present invention. For instance, in scenarios withslow varying SNR, the receiver 204 can invoke and transmit a feedbacksignal 214 only when the interleaver needs to be changed.

It should also be noted that information other than SNRs may be fed backto the transmitter 202 for other reasons, and may be exploited for ourpurposes. For instance, actual channel tap estimates may be fed back tothe transmitter 204, which can be used to condition the transmittedsignal 216 accordingly. The taps may be represented in the time orfrequency domain, and either can be easily manipulated to suit the needsof the present invention. Also, estimates of the noise level on eachtone or each slot may be fed back to the transmitter 204.

In another extension of the present invention, a multiple antennareceiver 204 can be used. This includes the case where a transmitter 202transmits a single signal or stream from a single antenna, or frommultiple antennas acting as a beam-former, or from multiple antennasacting as a transmit diversity system, e.g. Alamouti code or delaydiversity. At the multiple antenna receiver 204, the SNR can be computedper tone or per slot after combining the multiple antenna signals. Then,the rest follows as described above.

In yet another extension of the present invention, a multiple antennatransmitter 202 can be used, that could transmit multiple streams ofinformation. And, the receiver 204 would compute an SNR vector perstream where each SNR vector may be different because each stream may betransmitted differently. In this case, multiple SNR vectors are fed backto the multiple antenna transmitter 204 which then organizes eachstream's codewords in accordance with the schemes of the presentinvention.

Although multiple embodiments of the present invention have beenillustrated in the accompanying Drawings and described in the foregoingDetailed Description, it should be understood that the invention is notlimited to the embodiments disclosed, but is capable of numerousrearrangements, modifications and substitutions without departing fromthe spirit of the invention as set forth and defined by the followingclaims.

1. A transmitter that receives a feedback signal and uses data in thefeedback signal to adapt at least one of a coder, interleaver andmodulator located therein to organize information which is subsequentlytransmitted to a receiver.
 2. The transmitter of claim 1, wherein saidinterleaver adapts and uses a random error correction code to organizethe information which is subsequently transmitted to the receiver. 3.The transmitter of claim 1, wherein said interleaver adapts and uses aburst error correction code to organize the information which issubsequently transmitted to the receiver.
 4. The transmitter of claim 1,wherein said modulator and said coder adapt and use differentialmodulating and coding to organize the information which is subsequentlytransmitted to the receiver.
 5. The transmitter of claim 1, wherein saidinterleaver adapts and uses an interleaving pattern to organize theinformation based on a number of signal-to-noise ratios (SNRs) in thefeedback signal and when the number of SNRs is less than a code lengthassociated with the information then the interleaving pattern used toorganize the information is repeated.
 6. The transmitter of claim 1,wherein said interleaver does not use carriers or slots which areassociated with signal-to-noise ratios (SNRS) in the feedback signalthat are below a predetermined threshold where it becomes detrimental tosend the information to the receiver.
 7. The transmitter of claim 1,wherein said feedback signal includes a signal-to-noise ratio (SNR) foreach tone, hop or slot.
 8. The transmitter of claim 1, wherein TimeDivision Multiple Access (TDMA) with frequency hopping is used whensending the organized information to the receiver.
 9. The transmitter ofclaim 1, wherein Time Division Multiple Access (TDMA) without frequencyhopping is used to send the organized information to the receiver. 10.The transmitter of claim 1, wherein Code Division Multiple Access (CDMA)is used to send the organized information to the receiver.
 11. Thetransmitter of claim 1, wherein Orthogonal Frequency DivisionMultiplexing (OFDM) is used to send the organized information to thereceiver.
 12. The transmitter of claim 1, wherein Multi-Carrier CodeDivision Multiple Access (MC-CDMA) is used to send the organizedinformation to the receiver.
 13. A method for exploiting knowledge aboutchannel conditions in a wireless communications network, said methodcomprising the steps of: receiving, at a transmitter, a feedback signalfrom a receiver wherein the feedback signal contains data about a stateof a channel between said transmitter and said receiver; exploiting, atsaid transmitter, the data about the state of the channel in thefeedback signal to adapt at least one of a coding, interleaving andmodulating scheme to organize information that is subsequentlytransmitted to said receiver.
 14. The method of claim 13, wherein saidtransmitter uses the data about the state of the channel in the feedbacksignal to adapt the interleaving scheme which is suited for a randomerror correction code to position codeword bits associated with theinformation that is subsequently transmitted to said receiver.
 15. Themethod of claim 13, wherein said transmitter uses the data about thestate of the channel in the feedback signal to adapt the interleavingscheme which is suited for a burst error correction code to positioncodeword bits associated with the information that is subsequentlytransmitted to said receiver.
 16. The method of claim 13, wherein saidtransmitter uses the data about the state of the channel in the feedbacksignal to adapt the modulating and coding schemes to use differentialmodulating and coding to organize the information that is subsequentlytransmitted to the receiver.
 17. A communication system, comprising: atransmitter capable of transmitting a radio signal; a receiver capableof receiving the radio signal and further capable of processing theradio signal and transmitting a feedback signal containing data about achannel associated with the radio signal; and said transmitter capableof receiving the feedback signal and further capable of using the datain the feedback signal to adapt at least one of a coding, interleavingand modulation scheme therein to organize information that issubsequently transmitted to said receiver.
 18. The communication systemof claim 17, wherein said transmitter uses the data in the feedbacksignal to adapt the interleaving scheme which is suited for a randomerror correction code to position codeword bits associated with theinformation that is subsequently transmitted to said receiver.
 19. Thecommunication system of claim 17, wherein said transmitter uses the datain the feedback signal to adapt the interleaving scheme which is suitedfor a burst error correction code to position codeword bits associatedwith the information that is subsequently transmitted to said receiver.20. The communication system of claim 17, wherein said transmitter usesthe data in the feedback signal to adapt the modulating and codingschemes to use differential modulating and coding to organize theinformation that is subsequently transmitted to the receiver.
 21. Thecommunication system of claim 17, wherein said feedback signal includesdata about a signal-to-noise ratio (SNR) for each tone, hop or slot. 22.The communication system of claim 17, wherein said feedback signalincludes interleaving data.
 23. The communication system of claim 17,wherein said feedback signal includes data about actual channel taps.24. The communication system of claim 17, wherein said feedback signalincludes data about estimates of a noise level on each tone or slot. 25.The communication system of claim 17, wherein said receiver transmitsthe feedback signal only when the interleaving scheme needs to bechanged at said transmitter.
 26. The communication system of claim 17,wherein said receiver is a multiple antenna receiver.
 27. Thecommunication system of claim 17, wherein said transmitter is a multipleantenna transmitter.
 28. A base station, comprising: a transmitter thatreceives a feedback signal and uses data in the feedback signal to adaptat least one of a coder, interleaver and modulator located therein toorganize information which is subsequently transmitted to a receiver.29. The base station of claim 28, wherein said interleaver uses the datato adapt a random error correction code to organize the informationwhich is subsequently transmitted to the receiver.
 30. The base stationof claim 28, wherein said interleaver uses the data to adapt a bursterror correction code to organize the information which is subsequentlytransmitted to the receiver.
 31. The base station of claim 28, whereinsaid modulator and said coder use the data to adapt a differentialmodulating and coding scheme to organize the information which issubsequently transmitted to the receiver.
 32. The base station of claim28, wherein said feedback signal includes a signal-to-noise ratio (SNR)for each tone, hop or slot.